When a user buys a mobile telephone, the user often must subscribe to a service plan in order to make and receive calls with the mobile telephone. For example, the user might have to fill out a service order to subscribe to various basic and supplementary services from the network operator (alternatively called the carrier) of a mobile telephone network. An employee of the network operator processes the service order, entering information about the subscriber into a database for the network. After the information is entered, service is activated for the subscriber. This process can be fairly quick, and it works well when subscribers have personal contact with the employee of the carrier, as happens at a store run by the carrier.
When a mobile telephone is sold off-the-shelf at an independent retail outlet, however, the buyer may need guidance to activate service. Simply providing a special number on the packaging or manual for the buyer to call to activate service may not provide adequate guidance in some cases.
To facilitate distribution through independent retail channels, some existing mobile telephone networks support a single number origination (or “hotline routing”) feature for pre-activated subscribers. When conventional single number origination is used for a subscriber, any call originating from the subscriber (except 911) is routed to the same number. For a pre-activated mobile telephone, a user buys the mobile telephone off-the-shelf, powers on the phone, dials any number (again, except 911), and the call is routed to an activation center. The user then provides subscriber information, credit card information, subscription choices, etc. over the phone to personnel at the activation center to activate service.
Unfortunately, single number origination as used in certain existing mobile telephone networks does not work well in networks that follow the Global System for Mobile Communication [“GSM”] standard. In much of the world, mobile telephones operate according to the GSM standard. In fact, the GSM standard is becoming more popular in North America. To understand why single number origination (as supported in existing networks) does not work well in GSM networks, it helps to have some background knowledge about GSM networks
I. GSM Networks
The GSM standard is a collection of technical documents and agreements that address the network infrastructure for GSM service. FIG. 1 shows part of a generalized GSM network (100) according to the prior art. At a high level, the GSM network (100) includes a mobile station (120), a base station subsystem [“BSS”] (140), and a network switching subsystem [“NSS”] (160). In practice, a GSM network can include an arbitrary number of certain entities (e.g., mobile station, BSS, MSC) shown in FIG. 1. Moreover, for the sake of simplicity, FIG. 1 omits certain entities (e.g., operations and maintenance center, business systems). For additional information about GSM networks, see, e.g., Gunnar Heine, GSM Networks: Protocols, Terminology, and Implementation, Artech House, Boston (1999) and the GSM-related specifications referenced therein. Some telecommunications networks (e.g., third generation networks) extend the GSM architecture, complying with the GSM standard in various respects while enhancing service in other respects.
A. Mobile Station
The mobile station (120) includes mobile equipment [“ME”] (124) and a subscriber identity module [“SIM”] (122) (alternatively called a SIM card or smart card). To provide personal mobility for a subscriber, the SIM (122) is often detachable such that the subscriber can join the SIM (122) with another ME to receive/make calls or use other services with that ME.
The ME (124) (sometimes called the terminal) is a mobile telephone, other kind of telephone, personal digital assistant or other computer, or other device with GSM capability. A terminal identification, or international mobile equipment identity [“IMEI”], uniquely identifies the ME (124). The IMEI can be used to reduce trafficking in black market equipment.
The SIM (122) installs or inserts into the ME (124). The SIM (122) is usually the size of a credit card or a small plug-in unit. The SIM (122) includes a microprocessor and memory that stores subscriber-related data such as an international mobile subscriber identity [“IMSI”]. After a mobile subscriber integrated service digital network number [“MSISDN”] has been provisioned for the SIM, the SIM (122) may (but need not) store the MSISDN.
The subscriber identification, or IMSI, uniquely identifies the subscriber in any GSM system. The IMSI includes three parts: a mobile country code [“MCC”] consisting of three digits, a mobile network code [“MNC”] consisting of two or three digits, and a mobile subscriber identity number [“MSIN”] consisting of up to ten digits. For example, consider the IMSI 310555123456789. The first three digits “310” are the MCC for the United States, the next three digits “555” are the MNC for the home network of the subscriber within the country, and the final nine digits “123456789” are the MSIN identifying the subscriber within the network. The IMSI is not the subscriber's phone number. In general, the subscriber will never see the IMSI or need to remember it. For additional detail about IMSIs, see International Telecommunications Union [“ITU”] Recommendation ITU-T E.212.
Conventionally, a SIM vendor provides a set of GSM SIMs in bulk for a carrier. The carrier gets a file listing the IMSIs for the SIMs. The IMSIs each begin with the appropriate MCC and MNC for the carrier, and then include an MSIN.
The subscriber dialable number, or MSISDN, is assigned to the subscriber as the subscriber's phone number. The MSISDN and IMSI are never the same number and have different formats. (In contrast, in time division multiple access [“TDMA”] networks, the subscriber's phone number (the mobile dialable number) and the subscriber's mobile identification number [“MIN”] may be the same number.) A MSISDN includes a 1 to 3 digit country code, a 3-digit national destination code (i.e., an area code in the United States), and a variable length subscriber number. In North America, the subscriber's MSISDN is an eleven-digit number composed of the country code “1” and ten digits for the area code and subscriber number, for example, 12065551234. For additional detail about MSISDNs, see the relevant GSM standards or ITU Recommendation ITU-T E.164.
The mobile station (120) communicates with the BSS (140) across the Um interface (130), which is often called the air interface. The air interface (130) and other standardized interfaces shown in FIG. 1 facilitate interoperation between equipment from different manufacturers.
B. Base Station Subsystem
The BSS (140) includes a base transceiver station [“BTS”] (142) and a base station controller [“BCS”] (146) that communicate across the Abis interface (144). As shown in FIG. 1, the BSS (140) may include additional BTSs and BSCs. The BSS (140) communicates with the NSS (160) across the A interface (150).
The BTS (142) contains one or more radio transceivers that transmit and receive information over the air interface (130). The radio transceivers provide coverage to a geographic area and define a cell for the GSM network (100).
The BSC (146) manages the radio resources for the BTS (142) and other BTSs for specified cells of the GSM network (100). In particular, the BSC (146) participates in setup of various aspects of the air interface, (130), frequency hopping, and call handoffs from cell to cell in the GSM network (100).
C. Network Switching Subsystem
The NSS (160) performs switching for calls involving GSM network (100) users. The main component of the NSS (160) is the MSC (162), which operates in conjunction with the home location register [“HLR”] (164), the visiting location register [“VLR”] (166), the equipment identity register [“EIR”] (168), and the authentication center [“AuC”] (169). Depending on implementation and role in the GSM network, a NSS may lack certain components shown in the NSS (160) of FIG. 1 or share a component with one or more other NSSs. In one common configuration, each of multiple MSCs for a carrier is implemented with and controlled by a VLR, and each shares a single logical HLR for the carrier with the other MSCs. Depending on implementation, the database components may be distributed or implemented at a single location.
The MSC (162) performs many of the switching functions of a normal switching node of a public switched telephone network [“PSTN”] or integrated services digital network [“ISDN”] and (indirectly or directly) connects to the outside network (170). In addition, the MSC (162) provides functionality for handling mobile subscribers, including registration, authentication, location updating, call handoffs, and call routing. In some implementations, a MSC can perform a translation based upon the MSISDN of a calling subscriber. For example, in the MSC translation system of a MSC produced by Nortel Networks [“Nortel”], the TNUM selector allows the MSC to make a decision based upon the MSISDN of a subscriber who originates a call. MSCs from other vendors may provide the same or similar functionality.
The HLR (164) is a database that stores information about subscribers in the GSM network (100). Much of the information is relatively permanent, for example, information identifying a subscriber by IMSI and indicating services for the subscriber. Parts of a subscriber's HLR profile indicate whether the subscriber uses different bearer services for telephony, short message service, facsimile, and/or circuit-switched data, etc. A bearer service can have its own associated MSISDN, or several bearer services (e.g., telephony and short message service) can share a MSISDN. If a subscriber uses telephony bearer service, a corresponding MSISDN field of the subscriber's HLR profile needs a value for the telephony bearer service to work. In some implementations, each MSISDN in the HLR (164) must be unique—the same MSISDN cannot appear in multiple subscriber profiles.
Essentially, the HLR (164) stores information about a subscriber needed to load a VLR when the subscriber appears in the service area of that VLR. Particularly when the subscriber is not in his or her home system (i.e., roaming), the HLR (164) stores information about the current location of the subscriber, which typically includes the address of a VLR in which the subscriber is currently registered.
The VLR (166) is a database that stores selected information from the HLR (164) for subscribers currently visiting a geographic area serviced by the VLR (166). The VLR (166) uses the information to set up, control, and track calls and other subscribed services with mobile stations. For example, for a call involving the mobile station (120), an entry in the VLR (166) includes identifying information for the subscriber, MSISDN, information indicating the last known location area/cells for the mobile station (120), physical attributes of the mobile station (120), and services available to the subscriber. When a call is set up, the entry in the VLR (166) might also store the current cell for the mobile station (120), encryption keys, etc.
The EIR (168) and AuC (169) are used for authentication and security. The EIR (168) is a database that stores a list of IMEIs for MEs, and can be used to identify mobile equipment that has been stolen, etc. The AuC (169) is a database that stores keys and other information used for authentication and encryption.
D. Service Activation for a GSM Network
To make and receive calls using a GSM mobile station in a GSM network, a user activates service with a GSM carrier. For example, the user provides personal information such as name and address, billing information such as a credit card number, service choices for basic and supplementary services, etc. To activate service for the subscriber, a MSISDN is assigned to the subscriber for voice services and information for the subscriber is entered into the HLR for the GSM carrier.
E. Registration on a GSM Network
When a GSM mobile station is powered on, the mobile station (more specifically, the SIM) registers in a GSM network. A similar registration may occur when the mobile station changes locations in the GSM network or occur periodically to check the location of the mobile station.
After establishing a connection with a BSS, the mobile station sends a message to the MSC for the geographic area in which the subscriber is currently located. The message includes information identifying the subscriber. Initially, the identifying information is the IMSI, but for later registrations might be a temporary mobile subscriber identity [“TMSI”], which is assigned for use instead of the IMSI to complicate unauthorized tracking of mobile subscribers.
The VLR of the visited MSC may already have a record for the subscriber if the subscriber previously registered in the visited MSC. For example, the record includes identifying information for the subscriber, MSISDN, and supplementary service information. If the visited MSC has a record, the MSC authenticates the subscriber, and optionally authenticates the mobile equipment and assigns a new TMSI.
On the other hand, the VLR of the MSC may lack a record for the subscriber if the subscriber has never powered on the mobile station or has not registered in the visited MSC recently. In this case, the visited MSC uses the IMSI/TMSI to determine the subscriber's HLR. Through the subscriber's HLR (and perhaps a VLR in which the subscriber was previously registered), the visited MSC gets authentication information and authenticates the subscriber. The location of the subscriber is updated in the subscriber's HLR record and, if the subscriber was previously registered in another VLR, subscriber data is removed from that VLR. The VLR of the visited MSC then receives subscriber data for the subscriber, for example, identifying information for the subscriber, MSISDN, and supplementary service information.
F. Mobile Originating Calls in a GSM Network
When a GSM mobile station originates a call in a GSM network, the mobile station establishes a connection with a BSS and sends a message to the MSC in which the mobile station is registered. The message requests a connection with the MSC, specifying information identifying the subscriber (e.g., IMSI or TMSI).
After the MSC confirms the connection and authenticates the subscriber, the mobile station sends a setup message to the MSC that includes the number (e.g., the called MSISDN) dialed by the subscriber. The MSC routes the call to one or more other MSCs or switching nodes in other networks to set up the connection with the called party. This can involve locating a roaming subscriber, routing the call to another network, etc. Assuming the negotiations and connections between various components succeed and the called party accepts the call, the active phase of the call begins. When either party ends the call, the mobile station, BSS, and MSC release the resources used for the call.
II. Single Number Origination
To facilitate distribution of mobile telephones through independent retail channels, existing TDMA networks support hotline routing for pre-activated subscribers. In addition, several proprietary mechanisms have been proposed or implemented for hotline routing in GSM networks.
A. Hotline Routing for Pre-Activated Subscribers in TDMA Networks
The architecture of TDMA networks is similar in some respects to the architecture of GSM networks. For instance, a HLR in a TDMA network includes records with information about subscribers. A subscriber's profile includes a MIN as well as an electronic serial number [“ESN”] for the mobile telephone of the subscriber.
TDMA networks explicitly support single number origination. To implement this feature, the HLR profile for a pre-activated mobile telephone is provisioned with a MIN and ESN. In addition, the HLR profile includes a particular value (i.e., Origination Indicator=8) and the hotline number. When a user powers on the mobile telephone, the mobile telephone registers with a visited MSC. When the user dials a number, the visited MSC checks the profile for the pre-activated mobile telephone, detects the setting Origination Indicator=8, and routes the call to the hotline number. This feature is specified in Intermediate Standard 41 for existing TDMA networks.
B. Hotline Routing in GSM Networks
The GSM standard does not provide for single number origination as in TDMA networks. To address this problem, several mechanisms have been implemented or proposed which force originations from a particular GSM subscriber to a single hotline number by changing the subscriber's profile. In one common scenario, calls originated by an activated but delinquent subscriber are routed to a collections department. The subscriber is also barred from receiving calls, roaming, etc. Once the subscriber resolves the problem with the delinquent account, the hotline routing is removed.
These mechanisms are typically used for hotline routing of activated subscribers, not pre-activated subscribers. While several of the mechanisms could be used for pre-activated subscribers, there would be several disadvantages to doing so.
First, to the extent a mechanism uses settings or other features of a HLR profile for hotline routing, a MSISDN must be provisioned for the HLR profile. The MSISDN will not be in use for some period of time before service activation. In many countries, there are an insufficient number of available MSISDNs to justify assigning a MSISDN that will not be used for some indefinite period of time.
Second, to the extent a mechanism is proprietary to a vendor (for example, due to reliance on vendor-specific features, equipment, or messaging protocols), the mechanism ties a carrier to the vendor. This can prevent or at least complicate combining equipment from different vendors.
Nortel provides a non-intelligent network [“non-IN”], proprietary mechanism for hotline routing in GSM networks. Implementation requires Nortel MSC/VLRs and a Nortel HLR. To turn on hotline routing, a subscriber's HLR profile includes a Nortel Network Class of Service [“NCOS”] feature associated with a hotline number. The proprietary feature is passed as part of the subscriber profile in GSM mobile application part messages. The Nortel MSCs include translations from different NCOSs to different hotline numbers associated with the NCOSs. Thus, when the activated subscriber originates a call, the call is routed to the hotline number associated with the NCOS of the subscriber. The Nortel non-IN mechanism could be used for pre-activation hotline routing, but would require a profile in a Nortel HLR (with a MSISDN provisioned). Also, the Nortel non-IN solution will not roam outside of the configured network, nor will it work with another vendor's MSC/VLR or HLR.
Nortel also provides an intelligent network [“IN”] proprietary mechanism for hotline routing in GSM networks. Implementation requires Nortel MSC/VLRs, a Nortel HLR, and a Nortel service control point [“SCP”], which is a database that supplies translation and data needed for certain advanced services. To turn on hotline routing, a subscriber's HLR profile sets up the subscriber for virtual private network service with the SCP. In the SCP, the subscriber is provisioned as a virtual private network/hotline routing subscriber. The Nortel SCP is also configured with the hotline numbers. When a subscriber originates a call, the SCP provides a hotline number, and the call is routed to the hotline number. The Nortel IN mechanism could be used for pre-activation hotline routing, but would require a profile in a Nortel HLR (with a MSISDN provisioned). Moreover, at present, the Nortel IN solution does not easily roam outside of the configured network or work with another vendor's MSC/VLR, SCP, or HLR.
The GSM standard establishes four network-definable barring types that can be used to impose restrictions on subscribers. A network operator could use a mobile network-specific barring type in a subscriber's HLR profile to indicate to MSCs on the mobile network that hotline routing should be used for the subscriber. This mechanism does not easily roam outside the mobile network of the operator, since different carriers might use the same barring type for a different functionality. Moreover, to the extent the mechanism relies on settings in a subscriber HLR profile for hotline routing, it requires that a MSISDN be provisioned. In addition, the MSC translations required to implement the hotline routing can be relatively complex.